i really like the concept of this game. it's dang fun and a stiff challenge too, and in my books, that's the definition of a great game.
the game reminds me of McMillen's "The End is Nigh", in a way. they both have simple mechanics that you must master to traverse brutal landscapes. they're both difficult yet also fun, and have a great bit of charm in them.
there is a few things that could be changed for the better in this game. checkpoints in some of the longer levels would be nice, and having only your life count change between difficulty modes is a bit eh, but these problems barely affect the game's core, which is very solid.
this game well deserves a 5 star from me. what can i say? i'm a sucker for games that have the big 3, those being good concept, challenge, and enjoyment to be had.